The alpha-gal allergy is caused by a bite from the Lone Star tick, which carries the alpha-gal carbohydrate, also found in red meat. Alpha-gal is not known to cause sensitization under normal circumstances when humans eat meat. However, when alpha-gal enters the bloodstream during a Lone Star tick bite, antibodies develop that cause delayed allergic reactions to red meat several hours after ingestion. Symptoms can range from mild to life-threatening.

At this point, most cases are occurring in the southern and central U.S. states.